5IO Journal of AgriciiUural Research voi. x, no. lo 



According to Table V the addition of an alkali to the water greatly 

 increases the solubility of the quassiin powder — for example, the addi- 

 tion of the lye increased the solubility from five to six times, while the 

 addition of the soap increased it almost four times. It now remains 

 to be determined which one of the four solvents used in dissolving the 

 quassiin powder is preferable in the preparation of spray solutions. 



(l) ETHER AND WATER AS SOLVENTS 



Owing to the possibility that this quassiin powder may be impure, 

 the procedure detailed below was employed to test its purity. Schmidt 

 (39) says that quassiin is difficultly soluble in ether or water. Merck 

 (24) succeeded in separating a tasteless and supposedly inert substance, 

 which he called "quassol," from impure quassiin powder by using ether. 



Experiment i. — In an attempt to purify this supposedly impure quassiin powder, 

 5 gm. of it were extracted with 500 c. c. of ordinary ether for 24 hours, during 6 of which 

 the material was constantly shaken. After filtering, the amotmt of extract contained 

 in 100 c. c. of the filtrate was determined, and it was foimd that 1.8 gm., or 35 per cent, 

 of the quassiin powder went into solution in the ether. The ether-soluble residue 

 resulting was of a resinous character and not as bitter as the quassiin powder. Since 

 quassiin is somewhat soluble in ether, it would seem that this residue contained 

 both quassol and quassiin, but probably a greater percentage of the former, because 

 it was not so bitter as the quassiin powder. A small portion (0.57 gm.) of the resinous 

 material was extracted with 500 c. c. of water for 24 hours, during 8 of which the 

 mixture was constantly agitated. After filtering, the filtrate was sprayed upon 

 nastvirtium aphids, 58 per cent of which afterwards died (see Table VI). Since this 

 liquid was not very bitter and as it killed only about one-half of the aphids tested, 

 it may be inferred that the extract contained in it was mostly quassol. Since ordinary- 

 ether contains a trace of water, it was thought advisable to repeat this experiment 

 by using anhydrous ether for exhausting the quassiin powder. This ether extracted 

 45 per cent of the powder. A water extract of the ether-soluble portion killed 50 

 per cent of the nasturtium aphids and 54 per cent of the pea aphids. 



Experiment 2. — In this experiment an extract was prepared from the portion of 

 the quassiin powder not dissolved by the ordinary ether, described in experiment 

 I, by extracting an excess of it with water for 24 hours, during 8 of which it was con- 

 stantly shaken. After filtering the mixture, the filtrate, which was much more 

 bitter than that used in the preceding experiment, was sprayed upon nasturtium 

 aphids, all of which afterwards died. An extract was also prepared from the por- 

 tion of the powder not dissolved by the anhydrous ether, described in the preceding 

 experiment; this killed 95 per cent of the nasturtium aphids and 82 per cent of the 

 pea aphids. Since these residues did not contain quassol, it may be regarded that 

 the extracts used were practically pure quassiin. 



(2) WATER AS A SOLVENT 



Experiment 3. — One-tenth gm. of quassiin powder was macerated in 500 c.c. of 

 water for 2 hours with frequent agitation and the mixture was then filtered. Only 

 the undiluted filtrate and one dilution (1:5) of it killed practically all of the aphids 

 tested (see Table VI). 



Experiments 4 to 12. — The procedure of these was similar to the one just above, 

 and the results obtained are tabulated in Table VI. 



